Goldfish with ablation of the caudal half of the optic tectum will be tested by natural behaviors - feeding and avoidance - and by conditioned discrimination tasks. The chief question is whether the compressed retinotectal projection can mediate normal tectal functions. A second question is how the tectum contributes to shape-recognition abilities. This question is also approached by using a interocular-transfer test following training of fish to discriminate certain mirror-image pair of shapes. Because such transfer depends critically upon size of the shapes, we can test the hypothesis that a compressed tectal projection must result in "perceptual minification" of certain objects.